1. Field of the Invention
The present invention generally relates to a plotting system for plotting an object to be plotted by utilizing a computer-aided design (CAD). More specifically, the present invention is directed to a plotting method by way of a sketch input suitable for designing a die or mold in use of CAD/CAM (computer-aided design/computer-aided manufacturing system).
2. Description of the Related Art
To plot an object such as parts of an automobile on a monitor by utilizing a so-called "CAD (computer-aided design)" or "CAM (computer-aided manufacturing system)", various types of CAD/CAM plotting systems have been developed and commercially available. In the typical CAD plotting system, an operator initializes the CAD system to execute the plotting operation, e.g., a name of a plotted shape, a contraction scale, a position of an origin, a size of a technical drawing and the like. Thereafter, the operator manipulates a keyboard, a tablet, and a stylus pen so as to select various commands of the CAD language based upon instructions of a previously stored program, and thus to input various necessary data into the computer in the interactive mode, and also confirm the input data on the monitor.
As the conventional plotting systems, there are three typical plotting processes:
(1) In the first plotting process, all of the coordinate points are input through, e.g., the keyboard into the computer and displayed on the monitor, and then these coordinate points are connected by line segments, arcs and the like.
(2) In the second plotting process, all of the line segments, arcs, coordinate points and the like for constituting the shape of the object to be plotted are input so as to erase the unnecessary portions displayed on the monitor.
(3) In the third plotting method, the shape or pattern of the object to be plotted is searched from the previously plotted shapes, or patterns registered in the computer, taking account of the similarities, and thereafter the selected shape or pattern is copied in the memory of the computer. Then, corrections are partially made in the copied shape or pattern.
When the plotting process is completed, the subsequent plotting output process is performed. The graphic data are temporarily stored in the memory unit of the computer, and the desired shape of the object is plotted based upon the graphic data.
The above-described conventional CAD/CAM plotting systems are described in, for instance, "NIKKEI MECHANICAL" issued on July 30, 1984, pages 98 to 105.
Since such a graphic (plotting) data input operation of the shape/pattern relating to the object to be plotted is carried out by utilizing the CAD language in the conventional CAD/CAM plotting system, the following drawbacks are provided. That is, when plotting a drawing having a complex shape by the CAD system, the complex CAD operations are necessarily required. In other words, only skilled CAD operators can input such a complex plotting data. Otherwise, a lengthy plotting data input time is needed by a normal CAD operator, as compared with the hand-writing sketch method of the CAD system. More particularly, in the CAD plotting system employing a so-called "personal computer", a data capacity is considerably smaller than that of the powerful computer for CAD plotting system, and an amount of CAD language (commands) is also small. Accordingly, the CAD operabilities of the personal computer CAD plotting system are very degraded, which impedes the development of the CAD plotting systems employing small-scaled computers.
These problems belonging to the conventional CAD plotting systems are particularly enhanced in designing a die or mold by utilizing the conventional CAD/CAM plotting systems. That is, when designing a die or mold, only the above-described first and second plotting processes are utilized, because the number of similar die patterns is rather small. If the above-described third plotting process is utilized for designing a die or mold, all of the CAD-designed die patterns must be registered in the memory unit of the CAD plotting system, resulting in huge amounts of cost. Accordingly, this third plotting process is not a practical solution.